The overall objective of this research is to identify uterine molecular targets that influence the window of receptivity for embryo implantation. The rational for the proposed research is that a better understanding of uterine-derived mediators that influence the window of receptivity to implantation will offer multiple targets for uterine receptivity, which may in turn be used to determine appropriate times for embryo transfer in the in vitro fertilization clinic. In this proposal we will use wild-type mice to compare protein, lipid and metabolite profiles in isolated epithelial and stromal cells from prereceptive, receptive and nonreceptive (refractory) phases of uterine sensitivity to embryo implantation. Although current knowledge of lipid mediators correlated with uterine receptivity is relatively limited, lipid metabolites endocannabinoids and prostaglandins have been shown to play critical roles. An in-depth lipidomic characterization of a mouse model of uterine receptivity has never been undertaken. Our hypothesis is that regulatory networks in lipid metabolism could be serving as signaling hubs controlling previously uncharacterized targets; structurally complex lipids, lipid metabolic enzymes and lipid metabolites, with distinct roles in uterine receptivity. To explore this hypothesis, this project will utilize two unique technologies recently developed at Pacific Northwest National Laboratory for discovery and validation of molecular targets that influence receptivity for embryo implantation: 1) ultra-sensitive electrospray ionization ion mobility spectrometry-time of flight mass spectrometry (IMS-TOF MS) with advanced nano-scale liquid chromatography (nanoLC) methods and 2) nanospray desorption electrospray ionization (nanoDESI) imaging mass spectrometry. For nanoLC-IMS-TOF MS measurements, a complex mixture of peptides, lipids and metabolite samples will be prepared from appropriate mouse uteri cell types, and the platform will enable simultaneous quantification of all three classes of analytes. As our goal is to use these data to identify novel molecular targets with the potential to be directly associated with uteri receptivity, we will use our network and pathway-based data integration approach to focus on lipid signaling. These targets will be further validated with molecular assays in the Dey laboratory and by nanoDESI imaging mass spectrometry of uterine tissue sections to confirm cell type-specific expression. NanoDESI imaging will provide a unique look at lipids and metabolites, which cannot be visualized by in situ hybridization or immunostaining. This research will reveal the identity of specific molecular mediators, derived from and incurred by different cell types of the uterus, all of which influence embryo-uterine interactions during receptivity.